Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 50: [CPP] Organic Electronics and Photovoltaics III (Joint Session DS/CPP/HL/O)

O 50.4: Talk

Wednesday, March 24, 2010, 10:15–10:30, H37

Analysis of Metallic Conduction at the Interface of TTF and TCNQ Crystals. — •Viktor Atalla, Mina Yoon, and Matthias Scheffler — Fritz-Haber-Institut der MPG, Berlin, Germany

Organic materials are promising candidates for a next generation of electronic devices, since they offer a variety of new intriguing electronic phenomena while being environmentally friendly, low cost, and mechanically flexible. Here we study the interface of tetrathiofulvalene (TTF) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) organic molecular crystals which was found to exhibit metallic conduction [1] whereas the individual crystals are large band-gap semiconductors. Using quantum mechanical first-principles approaches employing the FHI-aims code [2] basic properties of monomers, dimers, and individual crystals are investigated. We construct interfaces between the two types of crystals and study the electronic band structures of the interface-induced states, which are relevant to the charge transport properties of the material. Depending on the relative orientation of the crystals the band structures were found to indicate metallic conduction at the interface. Furthermore the energetics of the polaron is investigated by calculating the geometry relaxation energy. For monomers of TTF and TCNQ this is found to be in the order of 0.1 eV, indicating that the electron-lattice interaction is an important parameter for charge transport in this system. [1] H. Alves et al., Nat. Mat. 7, 574 (2008). [2] V. Blum et al., Comp. Phys. Comm. 180, 2175 (2009).